I will forever be fond of "motherlode" in the Sims! It gave you 50,000 cash immediately. I still remember the day a friend showed this to me and it blew my mind. I used that code all the time to build the grandest of houses and fill it with all the most expensive crazy items. It also allowed my sims to paint and play instruments all day rather than go to work. They never worked a day in their lives... I only wish something like this was possible in real life!
I think this worked in both sims 3 and 4.
Bonus memory = another cheat code for the Sims was "testingcheats true"
Then various following cheat codes allow you to do things like:
access all world objects for building (not usually available in build or buy menus!)
Resize items
Move items without restrictions in the grid or put items on top of each other (where that usually wouldn't be possible)
These made for much more interesting and natural-feeling builds. Did I spend hours building? Yes. Did I then actually play the Sims in said building for very long? No π